This invention relates to a method and apparatus for treating a gaseous mixture in order to change the concentration of a component thereof. In another aspect, this invention relates to the selective absorption of an undesirable component of a gaseous mixture. In another aspect, this invention relates to an apparatus used for treating a gaseous mixture wherein said apparatus is submerged in the absorbent. Still another object of this invention relates to the contacting of an absorbent with a gas wherein the flow within the absorber is induced by means of the dispersion of the gas in the absorbent. In yet another aspect, this invention relates to the removal of carbon dioxide from a gas. Still another aspect of the present invention is the removal of carbon dioxide from a gas using salt water, e.g., sea water, as the absorbent. Another aspect of the present invention is the removal of carbon dioxide from carbon dioxide-containing natural gas. In yet another aspect, this invention relates to the removal of an impurity from a gas with the absorber being submerged in the absorbent and the impurity-rich absorbent is discharged at an absorbent depth such that the absorbent density at the level of discharge is very close to the density of the impurity-rich absorbent being discharged. Still another aspect of this invention relates to a method for removing impurities from a gas in which the absorbent flow rate is controlled by manipulating the liquid level in the top of the absorber. In still another aspect, this invention relates to the treatment of carbon dioxide containing natural gas obtained from an offshore well wherein the absorber is erected on the ocean floor and sea water is used to absorb the carbon dioxide.
The volume of natural and industrial gases treated for various purposes is continually increasing. Efficient and effective methods of treating gases, therefore, are very important to industry. The need for efficient and economical methods of treatment is especially important in the natural gas industry where the percentage of gas produced which requires treating will continue to increase as uncontaminated gas reserves are depleted.
One of the most common impurities found in natural gas is carbon dioxide. In many areas of the world, natural gas, predomonantly methane, is found associated with major amounts of carbon dioxide. When the carbon dioxide content exceeds about 10 volume percent, especially about 20 volume percent or greater, its removal by conventional means, such as amine absorption, becomes uneconomical due to the high energy consumption of the amine process required for regenerating the amine and due to the excessive size of the equipment necessary to remove such a large amount of CO.sub.2. The problem also exists in the handling of the large volume of removed CO.sub.2 unless a special situation exists where there is a worthwhile use for large amounts of carbon dioxide such as in flooding reservoirs for secondary or tertiary oil recovery. Also, it may be economical to use the gas as it is produced as a low heating value fuel if a suitably large demand for fuel gas for power generation or industrial purposes exists within a reasonable distance from the production site. Unfortunately, however, many of these gas reservoirs are in remote areas where no major demand for fuel exists, where carbon dioxide has no value and where construction of gas processing facilities is expensive. The cost of transporting the gas can be reduced, therefore, if the CO.sub.2 could be removed at the well, especially if the CO.sub.2 is present in a very high concentration.
Accordingly, it is an object of this invention to provide a method which enables more economical and convenient treating of gaseous mixtures.
Another object of the present invention is to provide an apparatus to be used in the treatment of gaseous mixtures.
Another object is to provide a process for treating a gas with an absorbent which does not require mechanical pumping of the absorbent or a high pressure absorber vessel.
Another object of the present invention is to provide a simple process for treating natural gas obtained from off shore wells.
Another object of the present invention is to save on cost of transporting gas from a well in a remote area, e.g., such as an offshore well 200 miles from land.
Another object is to provide a novel means for achieving a single stage of contacting of absorbent sea water with CO.sub.2 -rich natural gas in a cocurrent flow contactor.
Other objects, aspects, and the several advantages of this invention will be apparent to those skilled in the art upon a study of this disclosure, the appended claims and the drawing.